Yep I'd like to find out what it is "they" have in the TY's
Same engine I'm sure but you are spot on... radiator could be the only different item.

 

Not trying to threadjack, but to say thaks, My 91 would run 195-210 all day long unless uphills on hwy at 70, then slowly go to 230 and beyond. Checked belt today like purringraccon suggested, was not squealing and seemed tight untill I actually broke down and measured the slack. Tighted up to spec moncheche posted no issues today on same drive. Thanks.

 

I would just run 10-40 in your case. Its getting hotter, but, with 10-40 it would stay in place better at temp with the minimal clearances, which isnt a bad thing. whats the coolant sitch?

 

Can you explain a bit for me... 180-200 "foot" lbs??? from a torque wrench?? On the tightener bolt that pushes the adjustment pulley down?
And FSM... F_____ S______ Manual?
Thanks

 

FSM = Factory Service Manual

Mine is constantly on the verge of overheating at freeway speeds but does fine at slow speeds. If I try to maintain 70-75MPH I have to keep the heat on full blast to keep it from boiling over. I've replaced everything in the system so far after I had a plastic tank crack on the original radiator. I made sure to flush the block and heater core while I had everything out since I had used some of that radiator quick fix powder stuff to get home. I ran water through both directions with a garden hose for a few minutes till the water was coming out completely clear. The factory electric fan mount was cracked so I replaced that fan with an aftermarket one I had.

So far I've replaced:
Radiator (HD 3 core all metal unit)
Radiator cap (stock factory PSI rating)
Water pump (new stock type, not reman)
Upper and lower rad hoses
Serpentine belt
Thermostat 180* (with air bypass hole)
Electric fan (same size as factory one)
Radiator fluid - I tried the regular green stuff first then the orange stuff (not mixed though). Same temps with either type

The belt was squealing after the rad swap so I tightened it up shortly afterwards and haven't had any other problems with it (besides the temps) since then. I haven't replaced the clutch fan, but like I said, it cools fine at slow speeds. Any suggestions where to start to get this under control?

EDIT: I just came back in from checking the belt. It's in good shape but it's got about 3/8" to 1/2" movement when I push on it. I'll tighten it up tomorrow and see if that helps.

 

I tightened up the belt to 1/4" deflection and took it out for a spin. It did better and took longer for it to get hot, but it still got hotter than it should. If it hits the 220 mark on the guage it will boil over. I had to pull over and let it cool off a bit just before it got that far on the 10 minute test drive.

I ordered a new clutch fan today just because I don't know how many miles are on the one that's on there (147K on the odo). Probably won't help my problem, but it won't hurt either.

 

I've been reading as much info about possible solutions as I can find here, as well as all over the web. There was a good write up here -> http://jeephorizons.com/tech/xj_cooling.html, but some of the sources listed in the tech article are no longer correct. TurboCity.com apparently doesn't offer the CNC ported thermostat housing and high flow thermostat any longer according to their website.

I like the idea of the ported t-stat housing since the OEM version has a very sharp and restrictive (tighter that 90*) angle where the coolant comes from the top hose and feeds into the t-stat. So... I made a trip to the local junkyard and picked up a spare T-stat housing to play with. Here's what I came up with after about 30 minutes with a dremel and some sanding drum wheels.


I wasn't able to find a source for the high flow T-stat listed in the article yet. Does anyone here know where I could find one? I'm looking for a 180* version.

I also picked up a new HD clutch fan today. The old one still had some resistance to it, but the new one is definately stiffer. I tried to swap it out, but the new clutch fan is quite a bit thicker than the old one. I'll have to pull the radiator in order to be able to bolt it up. Anyway, that's where I stopped for now. I'll wait till I get all the parts I'm going to swap out so I can do it all at once.

Speaking of parts, next on the list of goodies to get is a high-flow water pump and maybe a Griffin all aluminum radiator (if I can swing it $$$). I'm thinking of stroking the 4.0 out to 4.6 or 4.7 next year, so the Griffin wouldn't necissarily be overkill.

 

Man, I can't believe with all your replacements and the 3 row upgrade that your still having overheating issues. Seems like the little jeep elves won't leave you be. I've been reading these cooling boards because i'm thinking of upgrading to the 3 row and i'm surprised at how many have issues at either slow speeds (typical) or either high speeds. Really surprised to hear about your high speed overheating. I wonder if your heater core is clogged and the water pump can't push water through it fast enough to keep it cool. That would be the last place out of what you have mentioned to look. Makes me paranoid about my ride. I just replaced my heater core this past year and let me tell ya, its a FULL days work.

 

The heater core seems to be just fine. When I replaced all that stuff, I flushed it both directions probably about 10 minutes each way till the water came out completely clear. Flow was good both directions showing no sign of any kind of restrictions in the core. The heat still works well and it noticeably lowers the temp when I turn the heat on the help suppliment the main radiator's cooling capicity.

I forgot to mention that on top of all that other stuff I'm also running an entire bottle of Redline Water Wetter in the coolant just to try to keep it under 220.

BTW: The rad cap is a new 16lb unit that was replaced with the radiator. I'm going to swap it out for a 18-19lb one to see if that might help. The all metal radiator should be able to take the extra pressure.

 

You have to think that a 3 core radiator has more surface area to cool. so quite possibly the factory fans just are not adequate enough to cool the extra surface area. Thats just what I have been told! I just hope I dont have any cooling issues

 

So I'm in the same boat as the most of you. After careful inspection/flushing of my system I can't reliably gain control of my overheating issue. I've contemplated purchasing a 3 row but I continue to see those who have done this and gain no real relief for the all to well known overheating issues these 4.0L have; esp. with the A/C on.

I posted this in another thread, hoping to spark some discussion, but no one seemed interested. For the sake of not letting this drop through the cracks; has anyone considered an air/water separator?

My 97 has a similar issue but does fairly well when I'm not using the A/C. I've often wondered if that might not be the solution. We all know the rumor that the 4.0 creates air pockets in its head and these systems are designed specifically for that issue; although typically that's a product of a water pump spending time at high RPMS. Here is a universal system a company I'm familiar with provides to the drifting community. We spend a lot of time in high revs so its a necessary addition for dedicated track cars. The concept can be applied to any cooling system though. The system is only $60 and can be found here I intend to buy one for my car but now considering a second one for the XJ. Hell, these are standard on some motors; like the Mazda RX-7 (rotary's are known for their cooling issues)



a diagram of how its supposed to work.

 

Interested.
Also familiar just didn't think of it. Of course S14Unimog pulling through for us all here.
Thanks.

Bump.

 

HESCO makes high flow stats, and housings......I've got one in the YJ...

 

I'm still working on my overheating issue, but not as fast as I'd like to. I just started college today so that's put the XJ on the back burner at least till the weekend.

 

I found a refence online that pointed to the RobertShaw high flow thermostat that was being sold by Turbo City. It's on Summit Racing's website, but it doesn't come up if you do a search by vehicle. The Summit part number is BRA-330-180 for the 180* version.

I ordered that thermostat and the GMB High Volume water pump (Summit part # GMB-110-1080P) today. When the order gets here I'll install everything and see how my temps look then.

If that doesn't work, next step will be to get an all aluminum radiator. I've already found a couple of less expensive ($150-$200 range) alternatives to the Griffin radiators by searching around the web.